The Internet widely used so far is a network constructed such that a service is requested and is provided in a one-to-one scheme between a sender and a receiver using the IP address. However, the use of the Internet has been continuously developed in a wide range of fields such as Internet high-definition TVs, Internet audio/video communications, Internet remote controls, Internet of Things (IoT) and the like. In reality, the Internet employing the one-to-one scheme has a limitation in scalability, security, service quality assurance due to the depletion of the IP address sapce.
A study is in progress on the future Internet to overcome the limitation of the Internet. The study on the future Internet can be based on an evolutionary approach and a revolutionary approach. The key aspect of the evolutionary approach is that the basic characteristic of the Internet is currently maintained as it is while service continuity is ensured and the improvement of the service is pursued. On the other hand, the key aspect of the revolutionary approach is that a network technology is created to fully meet the needs of a future society without being bounded or restricted by the current Internet technology.
Content-centric network (CCN) in the future Internet research is a new networking concept that the service is requested and provided based on a content name rather than a concept of requesting and providing the service in a one-to-one manner using the conventional IP address.
FIG. 1 is a functional block diagram illustrating a conventional content-centric network in accordance with the prior art, FIG. 2 is a functional block diagram illustrating a process in which a content is transmitted and received in the conventional content-centric network, and FIG. 3 is a functional block diagram illustrating a process of transmitting a content when a router to which a mobile terminal has access is changed in the conventional content-centric network.
A conventional content-centric network will be described in more detail hereinafter with reference to FIG. 1.
The conventional content-centric network includes a network 20 including a plurality of routers, a mobile terminal 10 connected to the network 20, and a content server 30.
The mobile terminal 10 is moved, and has access to any one of the plurality of routers included in the network 20 and transmits a content request message to the access router. The access router extracts an identifier of the requested content from the content request message and determines whether or not the requested content is stored and registered in the access router based on the identifier of the requested content. If it is determined that the requested content does not exist in the access router, the access router transmits the content request message to adjacent routers of the network 20 in a flooding manner. An adjacent router that has the requested content stored and registered therein among the adjacent routers or a source router that has access to the content server 30 providing the requested content transmits the requested content to the mobile terminal 10 in a reverse order to an order in which the request content message is transmitted.
Referring to FIG. 2, more specifically, the mobile terminal 10 transmits a content request message CR including an identifier of the requested content to an access router A if the requested content exists. The access router A compares the identifier of the requested content with a list of contents stored and registered in the access router A and determines whether or not the requested content exists in the access router A. If the requested content does not exist in the access router A, the access router A transmits the content request message to an adjacent router B, which in turn determines whether or not the requested content exists in the access router B in the same manner as in the access router A. If the requested content does not exist in the access router B, the access router B transmits the content request message to an adjacent router C of the adjacent router B. Then, the adjacent router C transmits the content request message to an adjacent router D thereof. The adjacent routers D is a source router that has access to the content server 30 providing the requested content. The source router D transmits a content response message CP including the requested content to the adjacent router C that has received the content request message. The adjacent router C maps the requested content included in the content response message CP to the identifier of the requested content and stores and registers the mapped content in the adjacent router C. Then, the adjacent router C transmits the content response message CP to the adjacent router B that has received the content request message. Then, the adjacent router B stores and registers the requested content therein in the same manner as in the adjacent router C and transmits the content response message to the access router A. Then, the access router A stores and registers the requested content of the content response message and transmits the requested content to the mobile terminal 10.
Meanwhile, a process of transmitting a content when a mobile terminal is moved and an access router of the mobile terminal is changed will be described in more detail hereinafter with reference with FIG. 3.
When the mobile terminal 10 has access to a router Q while moving during the reception of the requested content from a current access router A, the access of the mobile terminal 10 to the access router A is interrupted and the mobile terminal 10 has access to the new access router Q at a position where the mobile terminal 10 is moved. When the mobile terminal 10 connects to the new access router Q, it transmits the content request message to the new access router Q in order to continuously receive the requested content. Then, the new access router Q determines whether or not the requested content exists in the new access router Q based on the identifier of the requested content included in the content request message. If it is determined that the requested content does not exist in the new access router Q, the new access router Q transmits the content request message to adjacent routers sequentially in a flooding manner. An adjacent router I that has received the content request message transmits the content request message to adjacent routers D and P, respectively. The adjacent router D of the adjacent routers D and P is a path router included in a content transmission path before the mobile terminal is moved, thus has the requested content stored and registered therein. The path router D transmits a content response message including the requested content to the adjacent router I that has received the content request message, and transmits the content response message to adjacent routers that are present in the transmission path of the content request message in a reverse order to an order in which the content request message is transmitted.
However, if the requested content does not exist in the adjacent router P of the adjacent routers D and P, the adjacent router P continues to transmit the content request message to adjacent routers thereof until an adjacent router having the requested content stored and registered therein is retrieved.